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Date: Mon, 29 Jun 2015 20:18:58 +0300
From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To: linux-fsdevel@...r.kernel.org, Miklos Szeredi <miklos@...redi.hu>,
linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
linux-unionfs@...r.kernel.org
Cc: linux-security-module@...r.kernel.org
Subject: [PATCH 2/4] ovl: honor MS_NOEXEC flag at overlayfs mount
Overlayfs opens files directly at underlying filesystem. File->f_path.mnt
points to private clone of lower/upper mount. Thus MS_NOEXEC at overlayfs
mount has no effect because all checks are done against underlying mount.
This patch clears "noexec" at private lower/upper mounts (if noexec isn't
locked) and checks MNT_NOEXEC in overlayfs mount flags in ->dentry_open().
MS_NODEV already works correctly because kernel checks it before opening.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
Documentation/filesystems/Locking | 2 +-
Documentation/filesystems/vfs.txt | 2 +-
fs/open.c | 2 +-
fs/overlayfs/inode.c | 14 ++++++++++++--
fs/overlayfs/super.c | 14 ++++++++++++++
include/linux/fs.h | 3 ++-
6 files changed, 31 insertions(+), 6 deletions(-)
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 6a34a0f4d37c..f949910a9ff8 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -67,7 +67,7 @@ prototypes:
struct file *, unsigned open_flag,
umode_t create_mode, int *opened);
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
- int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
+ int (*dentry_open)(struct path *, struct file *, const struct cred *);
locking rules:
all may block
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 5eb8456fc41e..f5557f06ce12 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -364,7 +364,7 @@ struct inode_operations {
int (*atomic_open)(struct inode *, struct dentry *, struct file *,
unsigned open_flag, umode_t create_mode, int *opened);
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
- int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
+ int (*dentry_open)(struct path *, struct file *, const struct cred *);
};
Again, all methods are called without any locks being held, unless
diff --git a/fs/open.c b/fs/open.c
index e0250bdcc440..b619e28b2740 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -865,7 +865,7 @@ int vfs_open(const struct path *path, struct file *filp,
struct inode *inode = path->dentry->d_inode;
if (inode->i_op->dentry_open)
- return inode->i_op->dentry_open(path->dentry, filp, cred);
+ return inode->i_op->dentry_open(path, filp, cred);
else {
filp->f_path = *path;
return do_dentry_open(filp, NULL, cred);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 308379b2d0b2..b9a40c8dbd1e 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -10,6 +10,7 @@
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/xattr.h>
+#include <linux/mount.h>
#include "overlayfs.h"
static int ovl_copy_up_last(struct dentry *dentry, struct iattr *attr,
@@ -337,14 +338,23 @@ static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
return true;
}
-static int ovl_dentry_open(struct dentry *dentry, struct file *file,
- const struct cred *cred)
+static int ovl_dentry_open(const struct path *path, struct file *file,
+ const struct cred *cred)
{
+ struct dentry *dentry = path->dentry;
int err;
struct path realpath;
enum ovl_path_type type;
bool want_write = false;
+ /*
+ * After opening file->f_path.mnt points to private lower/upper mount.
+ * Here is the last chance to check flags at overlayfs mount.
+ */
+ if ((file->f_flags & __FMODE_EXEC) &&
+ (path->mnt->mnt_flags & MNT_NOEXEC))
+ return -EACCES;
+
type = ovl_path_real(dentry, &realpath);
if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
want_write = true;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 00e1d0b3abdd..64c3714acf38 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -923,6 +923,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
goto out_put_lowerpath;
}
+ /*
+ * Drop noexec at upper mount if allowed. We'll check
+ * MNT_NOEXEC at overlayfs mount in ovl_dentry_open().
+ */
+ if (!(ufs->upper_mnt->mnt_flags & MNT_LOCK_NOEXEC))
+ ufs->upper_mnt->mnt_flags &= ~MNT_NOEXEC;
+
ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
err = PTR_ERR(ufs->workdir);
if (IS_ERR(ufs->workdir)) {
@@ -951,6 +958,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
*/
mnt->mnt_flags |= MNT_READONLY;
+ /*
+ * Drop noexec at lower mount if allowed. We'll check
+ * MNT_NOEXEC at overlayfs mount in ovl_dentry_open().
+ */
+ if (!(mnt->mnt_flags & MNT_LOCK_NOEXEC))
+ mnt->mnt_flags &= ~MNT_NOEXEC;
+
ufs->lower_mnt[ufs->numlower] = mnt;
ufs->numlower++;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e351da4a934f..55c3edd9519e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1653,7 +1653,8 @@ struct inode_operations {
int (*set_acl)(struct inode *, struct posix_acl *, int);
/* WARNING: probably going away soon, do not use! */
- int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
+ int (*dentry_open)(const struct path *, struct file *,
+ const struct cred *);
} ____cacheline_aligned;
ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
--
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